A mobile communications network for which the 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short) standard organization defines a technical standard, hereinafter referred to as a mobile communications network or a 3GPP network, is currently the most commonly used wireless mobile communications network. A user accesses a mobile communications network by using a user equipment (User Equipment, UE for short), and makes an audio or video call with another user, sends a message, or logs in to the Internet to browse a web page or download data. As smartphones and some new data applications emerge, a capacity of the mobile communications network is faced up with growing challenges. Therefore, operators start to consider combining a mobile communications network with a wireless local area network (Wireless Local Area Network, WLAN for short), so as to provide better services for users.
Currently, a method for combining a mobile communications network and a WLAN is mainly as follows: A radio access network (Radio Access Network, RAN for short) of a mobile communications network sends, to a UE, information about access points (Access Point, AP for short) in a WLAN that covers, together with the RAN, a location of the UE; and the UE selects an appropriate AP according to the AP information and implements WLAN access by accessing the selected AP. When the UE undergoes a handover to another mobile communications network, for example, the UE moves to a new RAN, the UE disconnects from a WLAN connection with the original AP. After the UE is handed over from a source RAN to a target RAN, the target RAN sends, to the UE, information about APs in a WLAN that covers, together with the target RAN, the UE. The UE re-selects an appropriate AP according to the AP information that is sent by the target RAN, implements WLAN access again by accessing the selected AP, and further implements WLAN offload under the new RAN. WLAN offload (WiFi Offload) is to transmit, through WLAN access, service data that originally needs to be transmitted through a 3GPP access network, so as to reduce load on the 3GPP network.
It can be seen from the foregoing description that, when a UE undergoes a handover to another mobile communications network (that is, the UE is handed over from a source RAN to a target RAN) and after the UE is handed over to the target RAN, the target RAN needs to send, to the UE, information about APs in a WLAN that covers, together with the target RAN, the UE, so as to re-establish WLAN offload. As a result, time for re-establishing WLAN offload is relatively long, and data transmission interruption or packet loss will possibly occur, which affects service continuity.